Hundreds of Border Force officers at Heathrow Airport will launch a three-day strike on Friday in a dispute over rosters.
The Public and Commercial Services union (PCS) said more than 500 of its members working on passport control at terminals 2, 3, 4 and 5 are taking action in protest at new rosters being imposed.
The union said more than 250 staff face losing their jobs or being moved on to other work against their will.
Those who remain will have longer shifts, inflexible shift-swapping rules, no clarity on booking leave and no way to work around caring responsibilities, the PCS claimed.
A petition has been launched in support of the workers.
PCS general secretary Fran Heathcote said: “We call on all trade unionists and the public to support this petition and tell Border Force management to scrap this unwelcome and unworkable roster that has already caused misery to our members.
“PCS has repeatedly called for more flexibility in the new roster but management has refused to listen.
“Until they do, and they put forward proposals to improve the roster, then the dispute will continue.”
The strikes will be followed by three weeks of industrial action short of a strike, including a ban on overtime.
The Border Force staff staged a four-day walkout from the end of April in the same dispute.
The union said it expected disruption over the weekend as families return to the UK at the end of the half-term holiday.
The Government introduced a controversial new law last year aimed at ensuring a minimum level of service during strikes, including Border Force and the railways.
But it has not been taken up in strikes which have been held since the legislation was passed.
A Home Office spokesperson said: “We are aware of the planned strike activity at Heathrow this weekend.
“Border Force have robust plans to minimise disruption and keep the border safe and secure.
“We recommend that passengers check the latest advice from their operators before travelling.”
The Uefa Champions League final between Borussia Dortmund and Real Madrid is being held at Wembley Stadium on Saturday.
Fans of both clubs will be travelling to the capital for the game.